/*
 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
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 *
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 *
 *
 *
 *
 */

package java.util.zip;

import java.io.FilterInputStream;
import java.io.InputStream;
import java.io.IOException;
import java.io.EOFException;

/**
 * This class implements a stream filter for uncompressing data in the
 * "deflate" compression format. It is also used as the basis for other
 * decompression filters, such as GZIPInputStream.
 *
 * @author David Connelly
 * @see Inflater
 */
public class InflaterInputStream extends FilterInputStream {

  /**
   * Decompressor for this stream.
   */
  protected Inflater inf;

  /**
   * Input buffer for decompression.
   */
  protected byte[] buf;

  /**
   * Length of input buffer.
   */
  protected int len;

  private boolean closed = false;
  // this flag is set to true after EOF has reached
  private boolean reachEOF = false;

  /**
   * Check to make sure that this stream has not been closed
   */
  private void ensureOpen() throws IOException {
    if (closed) {
      throw new IOException("Stream closed");
    }
  }


  /**
   * Creates a new input stream with the specified decompressor and
   * buffer size.
   *
   * @param in the input stream
   * @param inf the decompressor ("inflater")
   * @param size the input buffer size
   * @throws IllegalArgumentException if {@code size <= 0}
   */
  public InflaterInputStream(InputStream in, Inflater inf, int size) {
    super(in);
    if (in == null || inf == null) {
      throw new NullPointerException();
    } else if (size <= 0) {
      throw new IllegalArgumentException("buffer size <= 0");
    }
    this.inf = inf;
    buf = new byte[size];
  }

  /**
   * Creates a new input stream with the specified decompressor and a
   * default buffer size.
   *
   * @param in the input stream
   * @param inf the decompressor ("inflater")
   */
  public InflaterInputStream(InputStream in, Inflater inf) {
    this(in, inf, 512);
  }

  boolean usesDefaultInflater = false;

  /**
   * Creates a new input stream with a default decompressor and buffer size.
   *
   * @param in the input stream
   */
  public InflaterInputStream(InputStream in) {
    this(in, new Inflater());
    usesDefaultInflater = true;
  }

  private byte[] singleByteBuf = new byte[1];

  /**
   * Reads a byte of uncompressed data. This method will block until
   * enough input is available for decompression.
   *
   * @return the byte read, or -1 if end of compressed input is reached
   * @throws IOException if an I/O error has occurred
   */
  public int read() throws IOException {
    ensureOpen();
    return read(singleByteBuf, 0, 1) == -1 ? -1 : Byte.toUnsignedInt(singleByteBuf[0]);
  }

  /**
   * Reads uncompressed data into an array of bytes. If <code>len</code> is not
   * zero, the method will block until some input can be decompressed; otherwise,
   * no bytes are read and <code>0</code> is returned.
   *
   * @param b the buffer into which the data is read
   * @param off the start offset in the destination array <code>b</code>
   * @param len the maximum number of bytes read
   * @return the actual number of bytes read, or -1 if the end of the compressed input is reached or
   * a preset dictionary is needed
   * @throws NullPointerException If <code>b</code> is <code>null</code>.
   * @throws IndexOutOfBoundsException If <code>off</code> is negative, <code>len</code> is
   * negative, or <code>len</code> is greater than <code>b.length - off</code>
   * @throws ZipException if a ZIP format error has occurred
   * @throws IOException if an I/O error has occurred
   */
  public int read(byte[] b, int off, int len) throws IOException {
    ensureOpen();
    if (b == null) {
      throw new NullPointerException();
    } else if (off < 0 || len < 0 || len > b.length - off) {
      throw new IndexOutOfBoundsException();
    } else if (len == 0) {
      return 0;
    }
    try {
      int n;
      while ((n = inf.inflate(b, off, len)) == 0) {
        if (inf.finished() || inf.needsDictionary()) {
          reachEOF = true;
          return -1;
        }
        if (inf.needsInput()) {
          fill();
        }
      }
      return n;
    } catch (DataFormatException e) {
      String s = e.getMessage();
      throw new ZipException(s != null ? s : "Invalid ZLIB data format");
    }
  }

  /**
   * Returns 0 after EOF has been reached, otherwise always return 1.
   * <p>
   * Programs should not count on this method to return the actual number
   * of bytes that could be read without blocking.
   *
   * @return 1 before EOF and 0 after EOF.
   * @throws IOException if an I/O error occurs.
   */
  public int available() throws IOException {
    ensureOpen();
    if (reachEOF) {
      return 0;
    } else {
      return 1;
    }
  }

  private byte[] b = new byte[512];

  /**
   * Skips specified number of bytes of uncompressed data.
   *
   * @param n the number of bytes to skip
   * @return the actual number of bytes skipped.
   * @throws IOException if an I/O error has occurred
   * @throws IllegalArgumentException if {@code n < 0}
   */
  public long skip(long n) throws IOException {
    if (n < 0) {
      throw new IllegalArgumentException("negative skip length");
    }
    ensureOpen();
    int max = (int) Math.min(n, Integer.MAX_VALUE);
    int total = 0;
    while (total < max) {
      int len = max - total;
      if (len > b.length) {
        len = b.length;
      }
      len = read(b, 0, len);
      if (len == -1) {
        reachEOF = true;
        break;
      }
      total += len;
    }
    return total;
  }

  /**
   * Closes this input stream and releases any system resources associated
   * with the stream.
   *
   * @throws IOException if an I/O error has occurred
   */
  public void close() throws IOException {
    if (!closed) {
      if (usesDefaultInflater) {
        inf.end();
      }
      in.close();
      closed = true;
    }
  }

  /**
   * Fills input buffer with more data to decompress.
   *
   * @throws IOException if an I/O error has occurred
   */
  protected void fill() throws IOException {
    ensureOpen();
    len = in.read(buf, 0, buf.length);
    if (len == -1) {
      throw new EOFException("Unexpected end of ZLIB input stream");
    }
    inf.setInput(buf, 0, len);
  }

  /**
   * Tests if this input stream supports the <code>mark</code> and
   * <code>reset</code> methods. The <code>markSupported</code>
   * method of <code>InflaterInputStream</code> returns
   * <code>false</code>.
   *
   * @return a <code>boolean</code> indicating if this stream type supports the <code>mark</code>
   * and <code>reset</code> methods.
   * @see java.io.InputStream#mark(int)
   * @see java.io.InputStream#reset()
   */
  public boolean markSupported() {
    return false;
  }

  /**
   * Marks the current position in this input stream.
   *
   * <p> The <code>mark</code> method of <code>InflaterInputStream</code>
   * does nothing.
   *
   * @param readlimit the maximum limit of bytes that can be read before the mark position becomes
   * invalid.
   * @see java.io.InputStream#reset()
   */
  public synchronized void mark(int readlimit) {
  }

  /**
   * Repositions this stream to the position at the time the
   * <code>mark</code> method was last called on this input stream.
   *
   * <p> The method <code>reset</code> for class
   * <code>InflaterInputStream</code> does nothing except throw an
   * <code>IOException</code>.
   *
   * @throws IOException if this method is invoked.
   * @see java.io.InputStream#mark(int)
   * @see java.io.IOException
   */
  public synchronized void reset() throws IOException {
    throw new IOException("mark/reset not supported");
  }
}
